In a typical inkjet recording or printing system, ink droplets are ejected from a nozzle at high speed towards a recording element or medium to produce an image on the medium. The ink droplets, or recording liquid, generally comprise a recording agent, such as a dye or pigment, and a large amount of solvent. The solvent, or carrier liquid, typically is made up of water, an organic material such as a monohydric alcohol, a polyhydric alcohol, or mixtures thereof.
An inkjet recording element typically comprises a support having on at least one surface thereof at least one ink-receiving layer. The ink-receiving layer is typically either a porous layer that imbibes the ink via capillary action, or a polymer layer that swells to absorb the ink. Transparent swellable hydrophilic polymer layers do not scatter light and therefore afford optimal image density and gamut, but take an undesirably long time to dry. Porous ink-receiving layers are usually composed of inorganic or organic particles bonded together by a binder. During the inkjet printing process, ink droplets are rapidly absorbed into the coating through capillary action and the image is dry-to-touch right after it comes out of the printer. Therefore, porous coatings allow a fast “drying” of the ink and produce a smear-resistant image. However porous layers, by virtue of the large number of air particle interfaces, scatter light, which results in lower densities of printed images.
Elements which comprise two distinct layers have been constructed which have an uppermost porous layer and an underlying swellable polymer layer. Such constructions suffer from poor image quality, as the rate of ink absorption in the upper porous layer via capillary action is orders of magnitude faster than absorption by ink diffusion into the swellable layer. This difference in absorption rates leads to unwanted lateral diffusion of ink in the uppermost layer when the ink fluid reaches the interface between the layers. This unwanted lateral diffusion of the ink is a phenomenon termed “bleed” in the art.
Inkjet prints, prepared by printing onto inkjet recording elements, are subject to environmental degradation. They are especially vulnerable to damage resulting from contact with water and atmospheric gases such as ozone. The damage resulting from the post imaging contact with water can take the form of water spots resulting from deglossing of the top coat, dye smearing due to unwanted dye difflusion, and even gross dissolution of the image recording layer. Ozone bleaches inkjet dyes resulting in loss of density. To overcome these deficiencies, inkjet prints are often laminated. However, lamination is expensive as it requires a separate roll of material.
Efforts have been made to avoid lamination and yet provide protected inkjet prints by providing an inkjet receiver having an uppermost fusible ink-transporting layer and an underlying ink-retaining layer.
U.S. Pat. Nos. 4,785,313 and 4,832,984 relate to an inkjet recording element comprising a support having thereon a porous fusible, ink-transporting layer and a swellable polymeric ink-retaining layer, wherein the ink-retaining layer is non-porous. However, there is a problem with this element in that it has poor image quality.
EP 858,905A1 relates to an inkjet recording element having a porous fusible ink-transporting outermost layer formed by heat sintering thermoplastic particles, and an underlying porous layer to absorb and retain the ink applied to the outermost layer to form an image. The underlying porous ink-retaining layer is constituted mainly of refractory pigments. After imaging, the outermost layer is made non-porous. There are problems with this element in that the ink-retaining layer remains light scattering and therefore fused prints suffer from low density, and the sintered outermost layer has poor abrasion resistance.
EP 1,188,573 A2 relates to a recording material comprising in order: a sheet-like paper substrate, at least one pigment layer coated thereon, and at least one sealing layer coated thereon. Also disclosed is an optional dye trapping layer present between the pigment layer and the sealing layer. There are several problems with this element in that the binder in the sealing layer is water-soluble which degrades the water resistance of sealed prints. While the sealing layer is porous, the dye trapping layer is not, which leads to bleed and degraded image quality.
It is an object of this invention to provide an inkjet recording element which can be printed with inkjet inks and fused to provide high density images. It is another object of the invention to provide an uppermost porous ink-transporting layer that has good mechanical integrity and is abrasion resistant. It is another object of the invention to provide an uppermost ink-transporting layer that is thermally fusible and thereby can be rendered water resistant. It is another object to provide an inkjet recording element that has immediately underneath the ink-transporting layer a fusible porous ink-receptive layer which has a greater affinity for the ink fluid than the upper layer, and retains inkjet colorants, and which can be subsequently fused. It is a further object of this invention to provide an element that has an uppermost porous ink-transporting layer and an underlying porous ink-receptive layer both of which can be fused to remove light scatter to provide excellent image density.